sharp s (Eszett)

John C Klensin klensin at
Fri Mar 7 21:22:47 CET 2008

--On Friday, 07 March, 2008 11:51 -0800 Michel Suignard
<michelsu at> wrote:

> Again, when I read
> ection-5.4 I see a set of rules that will require application
> to update when the repertoire grows. I am not exactly excited
> about it either, but it just means that browsers need some
> sort of self-update mechanism that most of them have anyway
> (including IE7). It is fairly clear that every browser (afaik)
> will require a serious patch to move from IDNA2003 to IDNA200x
> anyway (the bidi behavior change being another breaking
> change), so this does not create a specific issue on its own.


The key reasons for that update requirement is precisely the one
that Erik identified: one cannot know for sure what properties a
codepoint that might be assigned to a previously-unknown
location will have with regard to casefolding, compatibility and
canonical compositions and decompositions, and so on.  While we
all hope that there are enough reserved positions to head off
problems, one cannot even know for certain that a newly-assigned
codepoint will not have Right-to-Left properties that would
invoke the special bidi treatment.

On the other hand, those updates are not needed all at once.  If
the main change between Unicode 7.1 and 7.2 is the introduction
of several scripts for Martian languages, and you don't do
business on Mars or with multiplanetary Martian firms, there
might be few people who care how rapidly you incorporate those
changes.  The only firm requirement is that, at any given time
and with any given version of Unicode, your Unicode tables and
your IDNA ones reflect consistent versions.

Finally, assuming Erik's tests are correct (and I understand
them), MSIE7 is already being cautious about looking up
unassigned code points, putting it ahead of the curve on
IDNA200X rather than requiring retrofitting in that area.


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